Abstract

The development of multi-vendor, multi-terminal (MVMT) HVDC systems is expected to be important for the expansion of offshore electricity grids and the integration of offshore wind energy. However, the absence of a clear regulatory framework creates legal uncertainty, increases costs, and discourages investment. Interoperability is a key objective of EU energy law, but its implementation is not yet specifically operationalised in EU law for MVMT HVDC systems. The normative framework refers to a doctrinal analysis to determine the degree of openness required to achieve interoperability and to the regulatory measures through which openness could be implemented at EU level. This article examines how the principle of openness can be applied to enable interoperability through open standards and open-source software. It shows that openness is limited by competition law, intellectual property rights, and cybersecurity obligations. The article argues that interoperability requires a model of regulated openness consistent with EU legal requirements. It further highlights the need for EU-level harmonisation to define roles and responsibilities and to establish a coherent framework governing the development of MVMT HVDC systems.